Running keypad through SDO/SCL pins

I am attempting to use the SDO/SCL pins on the following keypad (https://www.jaycar.com.au/medias/sys_master/images/9107726270494/XC4602-dataSheetMain.pdf).

Using the following code;

int key=0;
int sclpin=31;
int sdopin=30;
int liquidVolume=0;


void setup(){
  Serial.begin(9600);
 
}
void keyInput(){
int keyRead(int sclpin, int sdopin); //returns key number or 0 if no key pressed
  pinMode(sclpin,OUTPUT);
  digitalWrite(sclpin,HIGH);
  pinMode(sdopin,INPUT);
  delay(2);                               
  for(int i=1;i<17;i++){
    digitalWrite(sclpin,LOW);            
    digitalWrite(sclpin,HIGH);
    if(!digitalRead(sdopin)){
     key=i;
   }      
  }
 }

void loop(){
  Serial.println(liquidVolume);     
   keyInput();       
  
    if ( (key > 0) && (key <= 9))
  {
    liquidVolume = liquidVolume * 10;
    liquidVolume = liquidVolume + key ;
    key=0;
          }
  }
}

The values given when the user inputs 1-9 on the keypad is to say the least very wrong. The intent is just to allow the input of multi digit numbers. I am a novice!

Post a link to the manual of that keypad or at least to the schematics of it to know which chip is used.